This invention relates to a melting apparatus for particulate material. More specifically, it relates to a gas fired apparatus for melting a freestanding pile of particulate feedstock in a cubic melting chamber.
Prior art apparatuses for melting particulate material generally utilized the off-gases of the melting process to preheat the feedstock by forcing the off-gases through the feedstock outside the melting chamber. To do this effectively, required the feedstock mass to be relatively homogeneous so as to provide uniform permeability and that this uniform permeability be maintained from the beginning of the preheating step to its end. Otherwise, the flow of off-gases would become channelized and overheat some portions of the feedstock while leaving other portions unheated. Localized hot and cold spots caused clumping which impeded the uniform movement of feedstock into the melting chamber. In severe cases, an entire layer of feedstock might coalesce and form a bridge across the feedstock entry to the melting chamber and thus stop the flow of material completely. Furthermore, where the prior art apparatus called for all the off-gases from the melter to be cycled through a column of feedstock in a vertical shaft preheater, any impairment or stoppage of the flow of off-gases would produce a corresponding impairment or stoppage of the melting process.